1. Field of the Invention
The present invention relates to a semiconductor fabricating method. More particularly, the present invention relates to a method of fabricating a capacitor.
2. Description of the Related Art
A memory function of a Dynamic Random Access Memory (DRAM) is carried out by controlling the voltage applied to the source region of a metal oxide semiconductor (MOS) transistor. Specifically, controlling the voltage applied to the MOS transistor entails controlling the flow of charges of a capacitor. In this manner, a read or a write operation is carried out, and thus the memory function of the DRAM is achieved. However, when the capacitor is operated, the charges in the capacitor are in a non-equilibrium state. In this non-equilibrium state, current leakage easily occurs. Therefore, it is necessary to refresh the capacitor periodically.
The refresh frequency depends on the charge-storage ability of the capacitor. As the storage ability of the capacitor increase, the refresh frequency for the capacitor is decreased. Thus, it would be advantageous to develop a capacitor having a high storage ability.
The storage ability of a capacitor can be increased by increasing the storage surface area of a capacitor or increasing the dielectric constant of a dielectric material. Since increasing the dielectric constant of the dielectric material usually involves material development, a long time is usually required for research and development. Thus, increasing the storage area of a capacitor by increasing the surface of bottom electrode is more expedient. The surface area of the bottom electrode can be increase by, for example, forming a hemispherical grained silicon (HSG) layer or increasing the height of the bottom electrode. In a fabrication process with a linewidth of 0.25 micrometers, or below, the surface area of a bottom electrode is increased not only by forming a HSG layer on the bottom electrode but also by increasing the height of the bottom electrode. However, the high bottom electrode often results in insufficient adhesion between the high bottom electrode and the contact node. This, in turn, causes the bottom electrode to lean or fall down. The quality of devices thus is degraded.